Electrical feedthroughs provide an electrical circuit path extending from the interior of a hermetically sealed housing of an implantable medical device (IMD) to the exterior of the housing. IMDs, such as cardiac pacemakers, implantable cardioverter defibrillators, neurostimulators, and physiological monitors, employ such electrical feedthroughs to make electrical connection with leads, electrodes or sensors located outside the IMD housing. A conductive path is provided through the feedthrough by a conductive feedthrough pin which is electrically insulated from the IMD housing. IMDs commonly operate in association with multiple leads, electrodes or sensors and thus feedthrough arrays including multiple feedthroughs have been developed.
IMDs can be susceptible to electromagnetic interference (EMI), which can interfere with proper IMD function. As such, capacitive filter arrays have been incorporated in the feedthrough arrays to filter each of the feedthroughs, shunting EMI at the entrance to the IMD. Examples of capacitive filtered feedthroughs for use with an IMD are generally disclosed in commonly assigned U.S. Pat. No. 5,870,272 (Seifried et al.) and U.S. Pat. No. 6,414,835 (Wolf, et al.), both of which patents are incorporated herein by reference in their entirety.
Feedthrough arrays used in IMDs must provide electrical connection across the IMD housing without compromising the hermeticity of the IMD housing. The feedthrough array generally includes a conductive ferrule that is welded to the IMD housing along an opening provided in the housing. Conductive feedthrough pins extending through the ferrule are supported and insulated from the ferrule by one or more ceramic insulators. A capacitive filter is electrically coupled to the feedthrough pins and the conductive ferrule to shunt EMI to the IMD housing serving as ground. A connector assembly is generally assembled over the ferrule and capacitive filter prior to welding the ferrule to the IMD housing. The connector assembly provides connector pads which facilitate electrical connection to the feedthrough pins. All of these components are assembled together in a manner that allows for leak testing of the feedthrough array to ensure that the feedthrough array will not compromise the hermeticity of the IMD housing.